S235JRG2 steel plate

S235JRG2 steel is a specific one and has no different classes. It was regulated in EuroNorm EN 10025 superseded by EN 10025-2 (2006) and the new designation is just S235JR. Both editions deal with "structural" steels.

The designation given is the symbolic one, the numerical designation of material is 1.0038.

ASTM steel S235JRG2 steel has different uses (can be applied to pressure service for example) even if it's a carbon steel too. The different grades refer to different strength grades. If you want to use EN steels according to EN 10025, there are some other designations for different strength grades (for example S275 or S355 which have a higher yield strength.)